Check out Paintstorm Studio It’s not horribly expensive and it has lots of options, very customizable brushes and also huge and diverse set of premade ones. It’s also more begginer friendly than photoshop (not really familiar with corel products but the ones I’ve used were just terribly confusing)
Also, shameless advertisment (while I don't get any money for it, further development of that tool are in my best personal interest) - have you tried PaintStorm Studio yet?
Hey, check out this thing, it's only 20 bucks and looks pretty fantastic.
http://www.paintstormstudio.com/
I use photoshop myself but I'm seriously considering giving Paintstorm a go with my Cintiq.